This invention relates to printing and more particularly, to a screen printing frame cleaning apparatus and method.
In some printing processes, for example, a silk screen printing process, a silk screen fabric is adhered or glued to a screen printing frame, and the silk screen fabric is used to produce an image on a substrate, for example, a CD disk label. As the images are changed, the current silk screen fabric is torn off or removed from the silk screen printing frame; and a new silk screen fabric with a new image is then adhered or glued to the frame. Normally, the same type of glue or adhesive is used, and it is not necessary that the old adhesive or glue be completely removed from the screen printing frame prior to the new silk screen fabric being glued thereon. Further, normally it is not a problem if the new silk screen fabric is glued over some older residual glue on the screen printing frame.
However, occasionally, the type of adhesive or glue being used is changed, for example, a solvent based glue is replaced with a water-based or latex glue. Further, in this example, the new water-based glue does not adhere or stick to the old solvent based glue. Therefore, before the new glue can be used, the surfaces on the screen printing frame on which the new glue is to be applied must be cleaned of the old glue. In some production environments, there are tens of thousands of screen printing frames used in production. Therefore, the task of cleaning the old glue from so many screens in daunting. Commercially available machinery is often used to clean screen printing frames. However such cleaning machinery is very expensive and is normally designed to clean large wooden screen printing frames. Thus, such machinery is less effective at cleaning smaller metal frames. Further, such machinery has additional disadvantages of using harsh chemicals in the cleaning process; and often, such chemicals require special handling and disposal.
To facilitate the adherence of a silk screen fabric, the surfaces of the screen printing frame to which the silk screen fabric is applied are often sandblasted to provide a textured surface. Further, to provide a more durable textured surface, the sandblasted surfaces are nickel plated. The old glue can physically be removed by mechanical methods such as sanding, brushing or grinding; however, all of those processes often damage or destroy the nickel plated finish. Further, the metal screen printing frames can be cleaned by using a manual scraper; however, such manual scraping is often performed inconsistently which results in damage to the nickel plated finish of the screen printing frame. In addition, the prospect of cleaning a large number of silk screen printing frames by a manual process is unacceptable.
Consequently, there is a need for a screen printing frame cleaning device and process that does not have the limitations and disadvantages of known devices and processes.
The present invention provides a simple, reliable, inexpensive, easy to use scrapping machine and a process for cleaning glue or adhesive from surfaces of screen printing frames. In addition, the scraping machine of the present invention cleans the frames relatively quickly with a minimum of labor. The scraping machine of the present invention is especially useful when a very large number of metal screen printing frames must be cleaned.
According to the principles of the present invention and in accordance with the preferred embodiments, the invention provides a scraping machine for scraping material off of a screen printing frame that includes a base adapted to support a screen printing frame. A first actuator is mounted on the base and has a carriage movable by the first actuator. A scraper blade is mounted on the carriage and contacts the screen printing frame. The scraper blade is moved across the screen printing frame by the first actuator, thereby scraping the material off of the screen printing frame. The scraping machine of the present invention is the only apparatus known to Applicant that can reliably clean thousands of metal frames without damaging the surfaces of the frames.
In one aspect of the invention, the scraping machine includes a scraper vibrator for imparting a vibration to the scraper blade. In a further aspect of the invention, the scraper vibrator is pivotally mounted to the carriage, and an actuator is used to pivot the scraping blade into and out of contact with a surface of the screen printing frame to be scraped.
In another embodiment of the invention, a method is provided of scraping material from a screen printing frame that includes the provision of a scraper blade. Next, a vibratory motion is imparted to the scraper blade with a scraper vibrator; and the vibrating scraper blade is then moved with a first actuator across a surface of the screen printing frame to scrape the material therefrom.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein.